In the process for manufacturing stainless steel, which is a kind of metal, molten iron is produced by melting raw materials in an electric furnace, molten steel is obtained by subjecting the produced molten iron to refining including decarburization for instance performed to remove carbon, which degrades properties of the stainless steel, in a converter and a vacuum degassing device, and the molten steel is thereafter continuously cast to solidify to form a plate-shaped slab for instance. In the refining process, the final composition of the molten steel is adjusted.
In the continuous casting process, molten steel is poured from a ladle into a tundish and then poured from the tundish into a casting mold for continuous casting to cast. In this process, an inert gas which barely reacts with the molten steel is supplied as a seal gas around the molten steel transferred from the ladle to the casting mold to shield the molten steel surface from the atmosphere in order to prevent the molten steel with the finally adjusted composition from reacting with nitrogen and oxygen contained in the atmosphere, such reactions increasing the content of nitrogen and causing oxidation.
For example, PTL 1 discloses a method for manufacturing a continuously cast slab by using an argon gas as the inert gas.